Whilst there are some parallels with the D&D of Windsor I think it's also important to highlight the differences.
As has already been said they received an allowance from the RF which had the benefit of applying certain ground rules to be adhered to if they wished to continue to enjoy that largesse.
It was also a very different age in respect of how people were perceived and perceived themselves.
The idea that the DoW would have to earn his own money would have been alien to him - moreover that he would debase himself by doing so by dabbling in "the arts". Their "star quality" was understood by both of them to rest in their royal titles and connections.
It is worth noting that Wallis got increasingly fed up with being expected to pander to her (man child) husband, keeping him entertained and essentially organising every aspect of his life. Away from the support of The Firm his lack of ability to live independently and thus expectations of his wife became very apparent. He may well have been happy in the marriage but the evidence suggests that Wallis was not.
In contrast the desire to earn their own money was central to H&M's reasons to step away from the RF because they believed their star quality as a couple eclipsed that of H's family.
They felt their "brand" was being thwarted within the institution and outside of it, had the opportunity to earn far, far more than they would gain within it.
They have embraced every single opportunity to earn $$$ irrespective of the consequences and/or optics.
Yet the evidence to date suggests they have been mistaken. Their deals have failed. Their popularity in polling is at an all time low.
H is turning up to the opening of an envelope if there is $$ to be had regardless of how foolish he looks (aviation award) or if it contradicts his own previously stated ethics/behaviours (Kennedy award).
Clearly there is a calculation that the sales from Spare are not going to keep the air con in Montecito running forever.
So what next? Trying to build bridges back with his family (I just can't see that happening especially with William)? Or an ever decreasing and danger spiral of selling himself to the highest bidder and/ or cultivating connections with people ready to fund his lifestyle.....now which other royal does that draw parallels with that didn't end well....